To investigate flavor changes in blueberry fruits during the green fruit stage, mid-ripening stage, and mature stage, headspace-solid-phase microextraction-gas chromatography-quadrupole flight time mass spectrometry in combination with odor activity value was used to analyze variations in the composition and content of volatile compounds of four blueberry varieties (LBS, ZB, FX, and SXL). The results showed 191 compounds, including 40 key aroma compounds, with terpenes being the predominant aroma components in blueberry fruits and exhibiting the highest number (53) and concentrations (42 455.36 μg•kg-1). Among the three developmental stages, the mid-ripening stage was identified as a critical phase for flavor transformation in blueberry fruits. Specifically, 149 (34 723.06 μg•kg-1), 128 (31 417.00 μg•kg-1), and 114 compounds (32 547.89 μg•kg-1) were detected in the green fruit, mid-ripening, and mature stages, respectively. In terms of compound concentrations, aldehydes and alcohols gradually increased, whereas ketones and esters gradually decreased. However, the concentration of terpenes varied differently across cultivars. The common key differential marker compounds in the varieties at the three developmental stages were hexanal and linalool. Flavor profile analysis indicated that LBS, FX, and SXL predominantly exhibited a floral aroma throughout development, whereas ZB displayed a strong floral aroma during the green fruit stage that evolved into a unique mixed aroma characterized by floral and herbal aromas as the fruits matured. This study provides a theoretical foundation for understanding the formation and variation of flavor during the development of blueberry fruits.